docs: def load_cookie(cls, request, key='session', secret_key=None):
          """Loads a :class:`SecureCookie` from a cookie in request.  If the
          cookie is not set, a new :class:`SecureCookie` instanced is
          returned.
  
          :param request: a request object that has a `cookies` attribute
                          which is a dict of all cookie values.
          :param key: the name of the cookie.
          :param secret_key: the secret key used to unquote the cookie.
                             Always provide the value even though it has
                             no default!
          """
          data = request.cookies.get(key)
          if not data:
              return cls(secret_key=secret_key)
          return cls.unserialize(data, secret_key)